Friday, 9 November 2012

Mirror lens

Mirror lenses were a fad during the 1970's.  They allowed a powerful zoom lens with a short barrel.  This made the lenses more managable.  But on the down side, these days all mirror lenses are manual only, so a bit of camera skill is required.
This is the Optika 500mm f6.3 mirror lens.  It comes with an adaptor to fit your camera, in this case a Nikon F-mount adaptor.  The camera needs to be set to manual and the ISO set to about 800 or 1000 manual.  Shutter speed will need to be between 100th and 250th of a second.
 In good light, it is quite easy to focus on relatively still subjects.  This is a squirrel sitting on the base of our bird feeder, taken from an upstairs window.
Moving subjects are more difficult as the manual focus has to be constantly adjusted to the possition of the subject and the margin for error is small.  A heron in flight was just to much for this kit when hand held.
However, with the assistance of a monopod, a heron across a lake is more of a certainty, when it is still.
A slight movement can upset the image sufficiently to make it blurred, To get around this, you can take several images in succesion and choose the best.
This is a better shot of the same subject, the best of 10 rapid shots.
A distinct advantage of this powerful lens is the ability to shoot through light vegetation and resolve the subject.  This grebe has a bank of rushes in the way, but the camera has resolved an image.  Notice the strange bluring effect of the "out of focus" reed heads caused by the lens's circular mirror.
All consided, I like this lens and the fiddle of having to use a manual light meter.  It took my back to the days of film cameras, when calculating the exposure was normal.  People who do not understand ISO, f-stop, shutter speed and focal length will find this type of lens very challenging.

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